{-# LANGUAGE MonadComprehensions #-}
{-# LANGUAGE TransformListComp #-}

quux' xs ys =
  [ ( x,
      y
    )
  | x <- xs,
    y <- ys,
    then group by
      -- First comment
      ( x
          + y
      )
    using
      -- Second comment
      groupWith -- Third comment
  ]
